Disk storage devices, especially disk storage devices utilizing one or more rigid magnetic data storage disks directly coupled to the rotor of a spindle drive motor and housed within a "clean room" chamber, typically use an "outer rotor" brushless DC motor for rotating the storage disks past data read/write heads. The heads write and read digital data on the surface of the disks. In an "outer rotor" brushless motor, a rotor having an annular permanent magnet surrounds a multi-pole stator that is mounted concentric with the shaft defining the rotation axis of the motor.
An outer rotor motor employs a rotor that encompasses the stator element. The rotor therefore requires a diameter that adds to the mass and angular inertia of the rotor and increases the time required for the motor to reach the operating speed, which may be 6000 RPM or higher, at the time of startup. The radially displaced mass also amplifies vibrations due to imbalances, especially at higher operational speeds.
It is an object of the invention to provide a disk storage device that utilizes a spindle drive motor that has a reduced rotary mass and angular inertia and accordingly reduces the time required to accelerate the storage disks to operating speed at the time of startup.
It is another object to provide a disk storage device that utilizes a spindle motor that is not limited by the diameter of the disk support hub in providing sufficient torque to rapidly accelerate a stack of many disks at the time of startup.
It is a further object to provide a disk storage device that has an increased diameter spindle support structure to enhance the rigidity of the disk axis.
Still a further object is to provide a disk storage device that reduces the amount of spindle run out caused by play in the support bearings.
Another object is to provide a disk storage device that achieves an enhanced air gap seal between the clean chamber in which the disks operate and the spindle motor elements.
Yet another object is to provide a disk storage device that reduces radially-displaced spindle mass and is capable of operation at higher speeds with lower vibration.